To make toner, resins often are suspended in an aqueous dispersion or emulsion. Two processes often are used to prepare latex, phase inversion emulsification utilizing an organic solvent to dissolve the resin or a solvent-free process relying on surfactant, neutralization agent and optionally water to dissolve the resin. The reactions can occur in a batch reactor or in a continuous reactor. Both of those processes have shortcomings and are inadequate for emulsifying high viscosity resin. Some commonly used resins have a softening point of at least about 120° C. generating issues arising from the loss of water during processing.
Solvent-free emulsification of polyester resin for emulsion aggregation (EA) toner has been described previously, see, for example, U.S. Pat. No. 7,989,135, the entire disclosure of which herein is incorporated by reference in entirety. That process, however, falls short when high viscosity resins are used; the higher viscosity of the resin at processing temperatures (e.g. at 90° C. or greater, for example, at about 100° C.) causes processing difficulties.
Therefore, new processes that produce latex, including at predictable and desired particle size, utilizing high viscosity resins in the absence of solvents are desirable.